Reporter Jürgen Todenhöfer Was Embedded With Islamic State. He Came Back Alive.

Jürgen Todenhöfer spent months in covert negotiations with Islamic State fighters over Skype, until he had reassurances from the very highest levels of the "Caliphate" that he would be safe in Iraq and Syria. The veteran German reporter then packed a small bag and departed for the most dangerous place on Earth.

Todenhöfer, speaking to ABC News, said he had made contact with up to 80 fighters before he decided to make the trip, building a strong enough bond with two of them to feel sure he would be safe. As sure as he could be.

The journalist and author, who has been one of the most prominent critics of Western intervention in the Middle East, said he was under no illusions that the Islamic State's fighters could easily renege on their promise to keep him safe while he travelled in the regions under their control, where he said he was "allegedly" the first Western journalist to visit Islamic State.

Jürgen Todenhöfer, the German reporter who was embedded with Islamic State for 10 days

The jihadi group's leaders were well aware he had been "extremely critical of Islamic State, here on Facebook and in the German press," Todenhöfer said. "I never underestimated the dangers of this trip."

Some of the most enduring and disturbing images of 2014 have been of journalists James Foley and Steven Sotloff, as well as aid workers David Haines, Alan Henning and Peter Kassig, murdered by a balaclava-clad IS fighter with a south London accent.

All of them, like Todenhöfer, had long records of support for Syrian and Iraqi civilians, and many of them had his anti-war credentials, and it did not save them from kidnap and death.

But Todenhöfer made it out alive, with an extraordinary story to tell. He raced on foot back on December 16 across the Turkish border, along a trail used by smugglers and carrying what he said felt like "1000-tonne weight on my back".

On his return, he issued a stark warning. "From my point of view this is the biggest threat to world peace since the cold war," he wrote in a detailed Facebook post. "We now pay the price for the inconceivable folly of George W Bush's attack on Iraq. The West has no concept of the threat it faces."

Arriving back in Germany, he said, his family burst into tears. His son Frédéric had "lost several pounds" in weight in the ten days he was gone, the reporter noted. Todenhöfer began writing about his experiences on his Facebook page this week, saying he had only just managed to reduce his stress levels in order to write.

"Of course, I knew that the risk was high," he wrote in German on Facebook, adding that he had also been afraid of US and Syrian bombings, describing circling US air raids when he was in the Iraqi city of Mosul. The apartment of his hosts in Raqqqa was also bombed, and Todenhöfer spent his last night there "in a bombed-out apartment, strewn with shards of glass".

"The West underestimated the risk posed by IS dramatically," Todenhöfer wrote, in the first of seven key bullet points he made about his trip. "The IS fighters are much smarter and more dangerous than our leaders believe. In the 'Islamic State', there is an almost palpable enthusiasm and confidence of victory, which I have not seen in many war zones."

The Islamic State, Todenhöfer said, have plans for mass genocide, and the deaths of all atheists, polytheists and religions that are not "people of the book" or Muslims who do not subscribe to their brand of Islam.

"The IS want to kill... all non-believers and apostates and enslave their women and children. All Shiites, Yazidi, Hindus, atheists and polytheists should be killed," Todenhöfer wrote. "Hundreds of millions of people are to be eliminated in the course of this religious 'cleansing'.

"All moderate Muslims who promote democracy, should be killed. Because, from the IS perspective, they promote human laws over the laws of God. This also applies to - after a successful conquest - the democratically-minded Muslims in the Western world.

"The only chance of this 'infidels', to escape the death, is voluntary repentance and voluntary conversion to 'True Islam'. IS is supposedly the only representative of this. And only before their countries have been conquered.

"Jews and Christians, as 'people of the book', are tolerated, but must pay a fixed protection tax of several hundred dollars per year."

Todenhöfer added that he "shouldn't need to emphasise that there was no agreement between me and IS on any of these points." But Islamic State is currently operating as a functioning totalitarian state, Todenhöfer said, "even if much of it does not meet our Western standards, and certainly not my standards".

From his encounters, he found many Sunni residents "unopposed to the new State... because they prefer it to the previous prevailing discrimination and oppression by the [former Iraqi prime minister] Maliki regime in Baghdad".

But he also called the version of Islam practiced by IS one that is "rejected by 99% of the world's 1.6billion Muslims".

"As a Christian who has read the Quran several times, it does not make sense to me, I do not know what any of the teachings of IS have to do with Islam," he said. "I got to know, above all, a merciful Islam from reading the Koran. 113 of 114 Suras begin with the words: "In the name of Allah, the most gracious and most merciful". I saw none of this mercy from IS."

But the strength of the fighters' beliefs in their interpretation of Islam can "move mountains", Todenhöfer continued.. "In Mosul, less than 400 IS-fighters beat 25,000 highly technically-equipped Iraqi soldiers. IS a territory conquered in a few months, which is larger than the UK. Al Qaeda is practically a dwarf," he observed.

A peshmerga fires a rocket in fight against Islamic State members in Sinjar district of Mosul

Todenhöfer described spending time at a reception centre for new IS fighters coming through Turkey from abroad, and said he saw up to 50 a day. The fighters were "not just young men, who had failed in their home countries... [but also] many successful, enthusiastic young people from the United States, England, Sweden, Russia, France, Germany, etc.

"One had only passed his first law exams a few weeks ago and had just been admitted to practice law in court. But he would rather fight for Islamic State."

Though much has been made of a recent Kurdish pushback against IS, which prevented them taking the Syrian border town of Kobane, Todenhöfer said the group is unfazed. "Occasional loss of territory does not seem to bother them, even if it is hyped by some of the media at the moment," he wrote. "It is normal in guerrilla war."

Todenhöfer, who says he is planning a book based on his experiences, said he could not have been sure of the truth about Islamic State until he saw it with his own eyes. "I had this guarantee of my security from the 'Caliphate'. I had no guarantee that promise was real. All my friends and family members have questioned its authenticity and tried to stop me from travelling. But such situations, I have to listen to my own instinct, what my inner voice tells me to do.

"I didn't go on this difficult journey, just because Pope Francis recently called for us to talk to IS," he said in an earlier post. "[I went] because after almost 50 years of experience I have always spoken with all sides. In Syria - where I was sharply criticised by some armchair commentators - I spoke with President Assad, but also with Al [Qaeda] and the FSA. I was in Afghanistan several times with President Karsai and with leaders of the Taliban. And during the Iraq war I was with the Shiite Government of Iraq and the [opposition] Sunni resistance."

Remarkably, the guarantee of safety was maintained, Todenhöfer said, though he notes that he was followed by the secret service and several of his 800 photos were deleted at the end of his trip. "It's called censorship," Todenhöfer said,

Todenhöfer said his exchanges with the fighters were not always cordial, but often "harsh and vociferous confrontations".

"It is not easy to argue with IS heavily armed fighters," he wrote, grimly. "Twice, the trip was certainly almost about to collapse. Given the daily danger for all those involved, the treatment was often fraught, but fair."

And Todenhöfer rejected any notion of Western military intervention helping to defeat IS. "The city of Mosul [in Iraq], with a population of three million, for example, is controlled by IS with about 5,000 fighters. To crush them with bombs means reducing all of Mosul to rubble and killing tens of thousands of civilians."

He posted one picture, with caption 'Do German weapons drops really serve peace?', of what he described as a "Heckler & Koch MG3 machine gun from Germany" for sale in Mosul, adding "someday this German MG could be directed to us. What madness!"

In a separate post, he called the terror group "a child of George W. Bush's illegal Iraq war.. [bombings] always are terrorist-breeding programs in the Middle East."

Todenhöfer said the only hope for the region was the resistance of moderate Sunni Arabs, but expressed pessimism that this could happen in the current climate.

The reporter said he could not "totally exclude" the risk of returning fighters coming to plan attacks in the West but said he thought it was not the main concern. "Returnees are considered losers 'who have not made it in the 'Islamic State'' So this is not the main risk, even though there was a plot by a returnee in Brussels. A greater danger may come rather from IS sympathisers who have not yet travelled to join the fighters."

"Groups such as Pegida [a German right-wing nationalist group leading marches of thousands against 'extreme Islam'] have their facts upside down. They are doing IS' work for them, they have a great interest in an escalation of conflict between Muslims and non-Muslims in Germany. IS confirmed me this to me several times."